Using a custom object to "hollow out" that same object?
What you need is a 'boolean modifier' which is already present in blender. 


Select your trapezoid by right clicking on it.


Create a copy of this trapezoid by pressing Shift+D.
Move it upwards by pressing 'G' and 'Z'
Scale it down a big by pressing 'S' and align is as shown below.






Now all you need to do is remove the top object from the bottom object. You can do this by adding a boolean modifier on the bottom big trapezoid.You can do this by selecting the bottom trapezoid and going to modifiers tab, click 'Add modifier' and selecting the boolean modifier as shown below.





Change the operation to 'difference' by clicking on the drop down menu.





Click the eye dropper tool and then click on the top smaller trapezoid.





Click on apply button.





Now you have your basket. You can now delete the top trapezoid by selecting and clicking delete.You will get something like this.